The invention relate to an analyzer for measuring impurities, such as an organic material, nitrogen compound and phoshorus compound contained in water, in particular, an analyzer adapting a wet oxidation decomposition system.
As a subject to be analyzed, there is mentioned extra-pure water widely used in the semiconductor manufacturing industry and pharmaceutical manufacturing industry, or for cooling in the nuclear power generation plant.
In the wet oxidation decomposition type analyzer, an oxidizing reagent together with a sample is added to an oxidization reactor in the oxidation decomposition process. Generally, since impurities are also contained in the oxidizing reagent, a sum of a measured value, i.e. true value, of a sample component to be measured and a background due to the impurities contained in the oxidizing reagent can be obtained as a measured value. Since these values can not be separated, it is necessary that the measured value, i.e. background, of only the oxidizing reagent without adding the sample thereto is separately measured, and the value is subtracted from the above-mentioned measured value to thereby obtain the measured value, i.e. true value, of the sample to be measured.
Since the result can be obtained by subtracting the measured value of only the oxidizing reagent from the sum of the measured value of the sample component to be measured and the background of the oxidizing reagent, in case the measured value, i.e. true value, of the sample component is sufficiently high when compared with the background of the oxidizing reagent, there is no problem. However, as in a case of measuring an extra-pure water, when the measured value or true value of the sample is especially lower than the background of the oxidizing reagent, there is a problem such that the accuracy of the measured result is extremely decreased.
In view of the above problems, the present invention has been made and an object of the invention is to provide a wet oxidation decomposition type element analyzer, wherein even if a concentration of a subject to be measured in a sample is low, it is possible to measure the concentration accurately without being disturbed by the concentration of the impurities of the oxidizing reagent.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In the present invention, an oxidization decomposition process for oxidizing only an oxidizing reagent in an oxidization reaction portion is provided right before a sample measurement. More specifically, an analyzer according to the present invention is a wet oxidation decomposition type analyzer, wherein the oxidizing reagent together with the sample is added to the oxidization reaction portion, and the oxidized component to be measured is measured at the analyzing portion to thereby obtain a concentration of the component to be measured. The analyzer includes a controlling portion for controlling operations for supplying the sample and the oxidizing reagent to the oxidization reaction portion, respectively. The controlling portion controls supplies of the sample and oxidizing reagent such that the oxidizing reagent is supplied to the oxidization reaction portion before the sample is supplied thereto, and then the sample is supplied thereto after elapse of a time during which the impurities contained in the oxidizing reagent are removed by the oxidization decomposition at the oxidization reaction portion.
First, the impurities contained in only the oxidizing reagent are removed through the oxidation decomposition at the oxidation reaction portion, and then, the sample is added thereto so that the sample is subjected to the oxidation decomposition with the oxidizing reagent from which the impurities have already been removed. Since the measured value obtained by the oxidization decomposition of the sample does not contain the background of the impurities contained in the oxidizing reagent, the true value of the sample component can be obtained.